The present invention relates to a modular die or mold and to a process for stamping or molding a plastic material using such die or mold to form a shaped article. In particular, it relates to a process for stamping a detergent bar and/or for molding an insert for a bar stamping die.
By xe2x80x9cdetergent barxe2x80x9d is meant a tablet, cake or bar in which the level of surface active agent, which comprises soap, synthetic detergent active or a mixture thereof, is at least 20 wt. % based on the bar.
In the manufacture of detergent bars, a preformed composition comprising all components of the bar is typically extruded from a nozzle to form a continuous xe2x80x9crodxe2x80x9d which is cut into smaller pieces of predetermined length, commonly referred to as xe2x80x9cbillets.xe2x80x9d These xe2x80x9cbilletsxe2x80x9d are then fed to a stamper or, alternatively, are given an imprint on one or more surfaces using, for example, a die of the same dimensions as the bar surface. The bar surface is hit with force by, e.g., a mallet or a die in the shape of a roller.
Stampers typically have a die formed in two halves each with a surface which contacts the billet during the stamping operation. These surfaces are adapted to close to a preset separation distance, thereby compressing the billet between the die halves to give the bar its final shape and appearance, and then separate. Excess composition is squeezed out from the die halves as they close. This is commonly referred to as xe2x80x9cflash.xe2x80x9d The flash is then separated from the soap bar by transferring the bar through holes in a xe2x80x9cdeflashing plate.xe2x80x9d
Conventional die stamping machines include xe2x80x9cpin diexe2x80x9d shaped machines in which a pair of opposing die members or die halves meet during a compaction step, and a xe2x80x9cbox diexe2x80x9d machine in which a pair of opposing die members stamp a bar held within a through-opening in a box frame but do not meet during compaction, the peripheral face of the bar being restrained by the box frame.
The die halves are often each provided with a die or ejector insert. These are normally held closed within the die halve by springs but can be pushed open by compressed air or mechanical means to assist in the release of the bar from the die. During closing of the die halves a vacuum can be applied to remove air trapped in the die cavity between the detergent bar and die surface and, in the case of rotary dies, this vacuum assists in retaining the bars in place during rotation.
Stamping of detergent bars using a die is carried out to give the bars a reproducible shape, smooth surface and/or to imprint a design such as a logo, trade mark or the like onto at least part of a surface of the bar.
However, as a result of die-blocking, i.e. amounts of residual detergent left on die halves which builds up during continued use of the dies, bars are often formed with visible imperfections on their surfaces or they may not release from the die surface. Numerous solutions to these problems have been proposed. One solution involves chilling the die halves during the stamping operation. Chiling uses valuable resources, particularly energy sources.
Another solution is described in GB-A-746 769 which discloses a die set which includes a die box and a pair of companion die members made of plastic materials comprising polymers with a specified modulus of elasticity. A disadvantage of this system is that a die release agent is necessary to prevent detergent from adhering to and building up on the dies and marring the surfaces of subsequently pressed bars.
WO 98/11194 is directed to a device for handling plastic materials such as a stamping device for stamping detergent bars, comprising at least two elastomeric coatings of different properties and/or compositions. Surface decorations such as uniform shape, smooth surface, design such as a logo, trademark or the like are said to be achievable in an easily reproducible manner in accordance with the invention. An advantage of thin elastomeric coatings is said to be that they can be easily applied in a factory to a conventional die with a built in logo. In describing the figure, it is said that a logo (not shown) may be formed on one or more of the die stamping surfaces if required.
Roberts, U.S. Pat. No. 3,534,440 discloses bodies of soap, detergent and the like which are pressed to final shape and/or size with indented or raised surface indicia in a die press. A detachable and replaceable section of embossed tape bearing the indicia is mounted on either an upper die pressing face or a bottom of a cavity or both. It is said that the invention may be used for synthetic detergent bars as well. Permanent indicia are said to restrict the dies to one usage run. Dies with replaceable inserts are said to be known. The thin embossable material embossed with the desired indicia may be attached by pressure sensitive adhesive means to one or more pressing faces of a pair of dies. It is said that while the tape seems relatively fragile, it does not rupture or deform under the high soap forming pressures and it is said to be believed that the air trapped in spaces opposite the embossed characters cooperates with inherent resiliency of the strip material effectively to uniformly cushion the strip to prevent destructive localized stress regions.
Cubbitt, U.S. Pat. No. 3,522,633 is directed to a die member comprising a rigid metal body having a forming surface provided with a panel receiving recess wherein a plastic design-bearing panel is molded in place. The panel has a surface that is substantially continuous with the die forming surface except for interruption by the design to be imparted to the article formed by the die. The panel is removable and replaceable by a different mold in place panel bearing a different design. The dies are for pressing of soap or like relatively soft material in bar cakes or any desired compact form.
An object of the Cubbitt invention is said to be to provide a novel soap pressing die structure wherein part of the internal soap contacting and forming surface of the die is a specially formed plastic panel for providing a desired design on the pressed soap bars. A further object of the invention is said to be a novel method of making a soap die member having a soap contacting and forming surface wherein an insert panel or the like is formed as by molding or casting into a recessed inset surface, the panel having an exposed surface which except for a design is essentially a continuation of the die pressing surface wherein the incorporated panel is removable for molding or casting a substitute panel. Should a different design be desired, panel 23 is displaced and replaced with another panel that is identical except for surface design. The replaceable panel may be formed in place on the metal die member using a master blank of hard non-deformable plastic. Preferably the panel material is a thermosetting material although it is said that thermoplastic material may also be used.
Pinto, U.S. Pat. No. 3,127,457 discloses a fluorocarbon film used as a release agent for molding polyurethane articles.
Krugg, U.S. Pat. No. 3,539,144 discloses a mold useful for producing polyurethane foams, which includes a structural mold shape and a coating of hot vulcanized silicon rubber disposed on the structural mold as well as a cold vulcanized silicone rubber deposited on the hot vulcanized silicon rubber.
Cavanugh, U.S. Pat. No. 4,035,122 discloses a soap saving device for compressing remnants of soap bars.
Austin, U.S. Pat. No. 4,076,207 discloses a food mold comprising a liner and a rigid holder wherein the liner has a rim for securement to the holder.
Roussel, U.S. Pat. No. 4,809,945 discloses a mold cavity for use in molding articles such as soap bars.
Watanabe, U.S. Pat. No. 5,332,190 discloses an elastic molding die composed of an elastomer laminate film, the innermost layer of which does not contain fillers.
In U.S. Pat. No. 5,269,997 it is proposed to provide each of two dies of a soap mold with an elastomeric septum stretched across their surfaces. Such a system would be complex to use at the speed required for commercial manufacture and a thin covering would be prone to tearing and logo reproduction would be expected to be poor.
WO 96/00278 (Adams et al.) is directed to a device for stamping a detergent bar having at least one bar stamping surface provided with at least one elastomeric coating having a thickness of less than 200 microns. An advantage of the device according to the invention is said to be that the elastomeric coating, being thin, can easily be applied in a factory to a conventional die with a built in logo. In FIG. 1, one die half is provided with a logo 14 on the bar stamping surface of a rigid member. This is also coated with elastomeric coating. In FIG. 5, the die cavity includes an injector bearing a logo.
Another solution is proposed in EP 276 971 and U.S. Pat. Nos. 4,793,959 and 4,822,273, which involve the use of two die members, each comprising a non-elastomeric and an elastomeric part. The elastomeric part, which contacts the soap bar during the stamping process, comprises an elastomer coating of at least 200 microns and having a modulus of elasticity within a specified range.
The manufacture of thick coated dies is a complex and expensive process. Therefore, it is highly desirable to maximize the working life of such coatings.
Hoppes, U.S. Pat. No. 3,474,498 discloses an indicia forming device for attachment to an article-forming surface portion of a mold, as for imprinting 3-dimensional medallion designs, or other indicia, in articles formed in the mold, as by blow molding methods. A thin, flexible pad or plate of rubber like plastic material is provided with appropriate 3-dimensional design configurations on one side thereof.
The Hoppes plate is positioned and adhered to an article forming surface portion of the mold. An object is to provide an indicia forming device which is quickly and efficiently interchangeable with like indicia forming devices to avoid undue expense and delays in the production of the blow molded articles. The medallion plate is a small rectangular piece of thermoplastic of thermo resin sheet material and it may be firmly, but removably adhesively attached to the article forming wall surface of the mold path. When replacement or renewal of the medallion plate is required, it may be peeled, scraped or otherwise removed from the mold cavity surface. It is said that the invention permits the dealer indicia to be changed as often as desired with only brief interruptions in production of the blow-molded articles. It is said that the medallion plate material may be any natural or synthetic rubber like material capable of resisting blow molded temperatures such as polyacrylic rubber.
Cerone, U.S. Pat. No. 4,781,564 discloses an apparatus for reforming soap bars. A lower shaping form and an upper shaping form, which may be replaced by another form to define a differently shaped or highlighted press chamber, are disclosed. The components are preferably formed of a durable structural material such as a hardwood or a molded plastic.
Dietterich et al., U.S. Pat. No. 5,413,472 discloses a molding device including first and second mold inserts.
Chittenden et al., U.S. Pat. No. 3,380,121 discloses a mold with replacable inserts so that the exterior appearance of a container blown within a mold may be changed without changing the basic shape and capacity of the container. The mold is for blow molding thermoplastic containers. It is said to be standard practice in the mold making industry to use inserts and molds for embossing figures, letters or designs on the article to be produced. Within recesses are provided removable metal inserts defining the walls of mold cavity and forming a surface which an article being blown is expanded. Means are provided for securing the inserts within the mold recesses so that the inserts can be easily and readily replaced within and removed from the recesses. It is preferred that the inserts be made of a metal having good thermal conductivity with respect to iron. The inserts themselves may be made of many different materials. The mold sectional body is usually produced from steel.
WO 99/23198 discloses a soap mold for pressing or stamping soap bars. Soap molds are described as having at least one dished cavity to accommodate one-half of the soap bar. An elastomeric part of the soap mold comes in contact with the soap mass to enable the soap to be more readily released. The soap mold of the ""198 invention is characterized in that it has a coating that is insertable into the cavity as a prefabricated detachable insert. The insert does not adhere to the mold, but can be removed from the mold substantially in one piece once it has become worn or damaged. The insert of the invention can usefully be provided with markings, for example the name of the soap. Usefully, the insert of the invention has at least one opening for an ejector pin which passes through the opening. The ejector pin ejects soap from the mold after pressing or stamping. Advantageously, the ejector is also coated. The ejector with the coating of the invention can also be formed as a plate or insert. Plastics which may be used to fabricate soap mold inserts can generally be elastomers or non-elastomers.
Bakewell, U.S. Pat. No. 170,464 discloses a jointed mold with an interchangeable plug for producing words, figures or designs upon the gross article.
The present invention is directed to a modular die or mold assembly comprising a platform, and at least one die or mold unit, wherein the said die or mold unit is releasably connected to the platform. Preferably, at lest two die or mold units, more preferably at least four die or mold units, are present per platform.
The assembly permits rapid charge of a mold or die, e.g., where it is desired to change the logo or other surface indicia on the article to be stamped or molded. Preferably the modular die or mold assembly is structured such that one of said platform and said die or mold unit includes a tongue and the other of said platform and die or mold unit includes a groove and the tongue and groove releasably connect the platform to the die or mold unit. More preferably, the die or mold unit includes the tongue and the platform includes the groove.
The present invention may be used as a die assembly to stamp detergent bars or it can be utilized for as a mold assembly for molding a detergent bar die elastomeric layer in which the molds are removable to allow rapid die logo changes. The invention is also directed to a process for its use of the die and/or assembly, especially for making soap/detergent bar dies.
The mold and die can be returned to the original design at no additional cost. A key benefit is the capability to rapidly redesign and/or customize soap bars at substantially lower cost.
The invention provides a low cost rapid system of changing soap bar logo designs. In the case of the molds, the modular mold unit of the assembly of the invention can be removed and replaced with alternatives of varying logo and surface designs. The elastomeric liners for the dies are then molded to provide new linings for the stamping surfaces.
The invention is also directed to multicavity dies in which entire cavities can be replaced to change surface indicia.
The invention reduces the time and cost currently required to deliver a bar logo change. Preferably, the invention allows bar logo flexibility at a fraction of the resource of the existing procedure.
The invention is also directed to the process of using the molds to make inserts for stamping soap/detergent bars of the invention and to the use of the dies to stamp soap/detergent bars.
An advantage to the use of modular dies and/or molds is that the surface ornamentation on the various cavities of a multiple cavity mold or die can be changed at will. For instance, it may be desirable to have different logos or other ornamentation on different detergent bars stamped at the same time. For instance, it may be desirable to provide various ornamentation for children""s detergent bars, e.g., various comic characters. Thus, the characters or other ornamentation could be varied from time to time, cavity by cavity. Also, damaged die or mold cavities could be replaced individual, cavity by cavity as the need arises for particular cavities.